Nongroxtnded ob metallic line-circuit system



April 15 1924. me. 15,817

R. H. BURFEIND NoNGnoUNDaD on METALLIC LINE cIncUIT sYs'rn Original Filed April 18, 1907 4 Sheets-Sheet] April 15 1924. Re. 15,817

. R. H. BURFEIND NCNGRQUNDBD OR METALLIC LINE CIRCUIT SYSTEM original Filed April 18, 196'? 4 Sheets-Sheet 2 April 15 1924.

- Re, 15,817 R. H. BURFEIND NONGROUNDED 0R METALLIC LINE CIRCUIT SYSTEM original Filed April 1s, 190'/` 4 sheets-sheet :s

Limi April 15 1924. Re. 15,817 R. HJ BURFEIND NoNGRoUNDED 0R METALLIC LINE CIRCUIT SYSTEM Oxfiginaiiled April 18, 1907 4 Sheets-Sheet 4 Y al( d Q www@ wmf@ www Rv 1l /WN n@ 1mm www mw @ik uw x NM1@ n@ Qww ik@ NT w 1 Q* \%\V r WWI; (MMWR www ,mw xm @no www wud A mr ww. t@ MN Q mwmu Reissued Apu-1.5, `19.24.

,uNi'raD STATES .y g Re 15,817 PATENT oFFics.

RAYIOND VBUBI'EIII'D, 0F CHICAGO, ILLINOIS, ASSIGNOB T0 AUTOIATIC ELECTRIC V OOIPAIY, A CORPORATION F ILLINOIS.

NONGBOUHDED B ITALLIC LINE-'CIRCUIT SYS'IEK,Y

Original application led April 18, 1907, Serial lo. 369,022. Renewed July 2, 1919, Serial No. 308,870.

rigiual No. 1,330,999, dated February 17, 1990'. Application for Serial No. 407,037.

To all whom it may concern: L

Be it known that I, RAYMONDH. BUn ramo, a citizen of the United States of America, and resident of Chicago, Cook l County, Illinois, have invented a certain new and useful Improvement in Nongrounded or Metallic Line-Circuit Systems, of which the following is a specification.

My invention relates to telephone systems l0 in general, but more particu arly to automatic or semi-automatic telephone exchange s stems, and especially to systems in which the common battery is employed for talking purposes. l In my rior application, Serial No. 369,021, lfiles April 18, 1907, for improvement in iionunded or metallic line circuit systems, issued as Patent No. 1,299,119, April 1, 1919, I have disclosed a telephone 2 exchange system having local batteries'at the subst-ations for operating the subscribers telephones, and 'in which automatic switches, such as selectors and connectors, are employed for automatica-ll extending 3| connection from a calling telep one line to a called telephone line, ysaid automatic switches being under the control of the calling subscribers. It will also be seen that in the said prior application the calling subscribersl exercise t e requisite contro over the exchan apparatus without the necessity of emp oying operating grounds at the substations-that is to say, the exchange apparatus is controlled entirely by circuits including both sides of the telephone line, and no ound circuits are employed between the clinge and the substations. AsA stated, however, in the said prior application the subscribers telephones are supplied -with current from local batteries, and the current from the central battery or batteries is only employed for controllin the operations of the switches at the ex My present invention, therefore, contem-M plates, broadly, an exchange in which the current for talking pu oses is derived from the central battery orrgatteries from which current is supplied for o rating the selectors and connectors o1' ot er switches, and in which no operating grounds are necessary at t-he subscribers telephones, whereby the line circuits over which current flows for both talking and switching purposes do v,the called substation A', #2220,

reissue le'd August 30, 1920.

not include the ground between the exchange and thesubstations. With such arrangement each calling subscriber uses both sides of the line for calling, as well as for talking, and the automatic connection of the calling telephone line with the called telephone line is accomplished by current derived from the same battery or batteries from which current is supplied for operating the switches, and no grounding line is necessary at the substations in order to control the automatic switches. In this way I provide a common battery automatic telephone exchange system which is free from operating grounds outside of the exchange or central station, at least so far as the control of the automatic switches is concerned.

I also provide certain details and features of improvement and combinations tending to increase the general eilciency and serviceability of a system of this particular character, and which may be found to beuseful in various connections.

of the' In the accompanying drawings, Fi l 1 and 2 taken together show two su tions A and A in a telephone system connected by means of central ollice switching apparatus embodyin the principles of my inven tion. The cal ing substation A, #5000, has i allotted to it the first-selector switch C, and has allotted to it the first selector switch C', both of which are alike. At D there is shown diagrammatically a second-selector, and at E a connector switch. A central battery having its positive terminal preferably grounded is shown at B.

Fig. 3 is an` enlarged detail view of thev substationv mechanism.

Figs. 4 and 5 are detail views of part of the mechanism shown in Fig. 3.

Figs. 6, 7 and 8 are detail views of thel substation impulse spri i Figs. 9, 10 and-11 are detail views of the release relays of vthe selector and connector switches. I

Fig. 12 is a diagrammatic view of the talking circuit between two substations. v

The substation A maybe of any suitable or approved type. The one in connection with which I have elected t0 illustrate my invention comprises a receiver 2,11 switchs rings 11 and 35 likewise being 1n multiple.v

e springs 17 and 16, known as the vertical impulse springs, are separated; while the spr' 18 and 19, known as 'the rotary impu se springs, are maintained in contact,

as well as the springs 32 and .33. The cam-V arm 4, furthermore, maintains the spring 6 away from `the spring 8'L and in cpntact with the spring 7, with the result that only the rin 9 is bri hookV is d'own. When the subscriber removes his receiver `from the switch-hook he causes a change in the circuits by shitin the spring 6 away from the spring 7 an into engagement with the spring 8*, as soon as the cam-arm 4 passes out of engagement with the spring v6. The result is that the .ringer 8 and condenser 9 are disconnected from across the line, and instead a high resistance coil 29 is bridged. across the line. Furthermore,l as soon as the cam-arm leaves the sprin '10, with which it normally engages, the said spring 10 flexes into enment with the spring 11, thereby bridgmg the transmitter 12 in serieswith the primary winding 14 of the induction-coil 13 across the line in multiple with Vthe .high resistance coil 29. The spring 10 is, however, so adjusted in relation to the locking cam 21 that when the dial is rotated the locking dog 20, upon raising the locking cam 21 a trifle, causes the said locking cam 21 topress the spring 10 away from the spring 11, thus again breaking the transmitter circuit. The induction-coil 13 is, of

. course, provided with the usual secondary winding 15 whichis closed in a local series circuit with the' receiver 2. The springs 16 and 17, known as the vertical impulse springs, and the springs 18 and 19, known as the rotary impulse springs, are operated through the medium of a dial (not shown) which is secured to the shaft upon which is mounted the locking do 20. The said locking dog 20, as is usua ly the case, is ock the dial while the receiver isn adapted to on the switch-hook in order to prevent its rotation. y

0n the aforesaid shaft there is mounted an impulse whee122 upped on its periphe with theV so-cal ed vertical impulse Y teeth 23 and with one rotary impulse tooth 24 (Figs. 6, 7 and 8). The said impulse wheel` is designed for o rating the impulse springs 17 and 18. he rotary impulse r 8 in series with the condenser,

across the line while the switch-V scriber is cal teeth are-so arranged that when the dial is rotated the impulse spring 17 is not carried into contact Awith the spring 16, but f as the dial returns7 first the vertical teeth press the vertical impulse springs 17 into contact with the spring 16 one or more times, and after they have completed their work the rotary impulse tooth 24 carries the rotary impulse spring 18 out of engagement with the spring 19 once.` In this operation the high resistance coil 29 'is sliort-circuited each `tiiiie the springs 16 and 17 are pressedinto' contact, and then when the springs 18 and 19 are momentarily disengaged, the circuit through the substa- /tion is interrupted.

With the arrangement shown it will rbe evident that the transmitterV circuit, which is' opened, as stated, as soon as the dial is turned, remains open as long as the sbling, and must be closed at some time before the called subscriber answers. This closure of the transmitter circuit is accomplished byl mechanical means when the dial is operated for the'last digit. A ratchet mechanism advances one step each `time the dial is rotated once, and upon the last'operation of the dial said mechanism reaches a point that closes the springs 34 and into contact and restores the transmitter circuit. The same operation that closes the springs 34 and 35 opensV the springs 32 and 33, whereby the high resistance coil 29 is disconnected from the line. In detail the device by whichV the above is accom lished is as follows: Upon the shaft 18 Fig. 3), on which are mounted the dial,-

the impulse wheel 22 and the lockin dog 20, there is loosely fitted a disk or whee 30 provided with sultable teeth upon its periphery, which teeth are adapted to e engaged at certain times by the pawl 38. As shown, this paw] is pivoted at the point 39. The said disk 30 is controlled `by a suitable spring 47 which is adapted to restore the disk 30 to normal position each time that the said disk is released. The said disk 30, furthermore, carries at a suitable int upon its periphery an insulating tip or nger 31 which is adapted to engage the spring 32 when the disk 30 hasy been advanced to a certain point. By thus engaging and raising the spring 32 the connection is broken through the spring 33, and at the same time -the springs 34 and 35 are carried into contact, as already explained. The pawl 40, which is pivotally secured at the point 41 to the locking dog 20, provides means whereby a third pawl 42 is operated to rotate the lwheel 30. When theV of which there is the pawl 43. The coilspring 44 is provided for returning the pawl 40 to normal position, so that on the return pawl 43 to return to en I teeth of the wheel 30, w

ber 42. As the locking dog approaches its normal rposition the pawl passes out of eng ment with the member 42; andthe lmem r 42, due to the tension of the spring 45, returns to normal position against the ll sto 46. At any time that the switchhook is owered, after the disk 30 has been advanced, the cam-arm 5 passes out of engagement with the locking cam 21 and permits the latter to fall upon the end of the pawl 0 38. The cam 21 is provided with a suitable retracting spring 21l having sulicient power to carry the awl 38 out of en agement with the teeth of ,lie wheel 30, which latter, owing to the tension of the spring 47, returns to u normal position with the pin 48 against the stop 49, as shown in Fig.4 3. In Fig. 5 the' ratchet mechanism is shown in its final operated positionthat is, after the subscriber has completed a call-the mechanism ha 'ng been operated four steps, and the bus ng 31 having pressed the spring 32 out of engagement with the spring 33 and carried the spring 34 into engagement with the spring 35, andthe member 42 and the pawl 43 are shown in vthe act of disengaging from the` pawl 40 and about to return to normal sition against the stop 46. 'Ihe means w ereby a subscriber may si al a called subscriber com rises the ush utton 25 which,when presse carries t e spring 26 out of engagement with the'contact point 27 and into engagement with the contact point 28, whereby -the line conductors 36 and 37 may be connected in series through the resistance coil 29. The first-selector switches in the system may be of any suitable or approved type, for example of the general type' described in United States Patent No. 815,321, granted March 13, 1,906, to Keith, Erickson and Erickson. The selector C, as shown, is a modified -form of the selector described in said selector patent. The switch shaft 50 carries the vertical and rotary wipers 51 and .52, respectively andv the private wiper 53.

Said shaft is also equipped with a set of circular teeth on the upper part comprising any suitable number. The said shaft wipers are ada ted to work in conjunction with the line anI private banks of the switch, but

w normally rest two steps below the first level ofthe bank contacts. The side switch is well known and comprises the side switch wipers 54, 55, 56, 57 and 58, which may be as the vertical, rotary and private side switch wipers, rotary magnet wiper and re- By means of before the shaft has rotated to disengage the designatedv lease wiper, respec tivel The side switch is under the control of thye and when the side switc is in normal or first position the wipers 54, 55, 56, 57 and 58y occupy the'contact points 59, 60, 61, 62 and 63, respectively. In the'second position they rest on'the contact points 64, 6,5, 66, 67 and 68, respectively, and in the third ition the contact lnts `6970,.\71, 72 an 73 are engaged by eir respective wipers.` Through the medium of the vertical line relay 74, and while the side Switch is in first position, the subscriber controls the vertical magnet 75, which latter operates to raise Ithe switch shaft 50 wipers .51, 52 and 53 vertically. the rotary line relay 76, and

springs 77 and 78, the subscriber controls thel private magnet 79 and therefore, the side switch. While the side switch is in second lposition the rotary magnet 80 is energized, which magnetv operatesto carry the switch` shaft 50 and wipers 51, 52 and 53 in a rotary direction. The relay 82'providesthe means whereby the vsubscriber controls the release magnet 83, while the side switch is in first or second position. If the side switch asses to the third position, then, since the se ector C is of the trunk-release type, the selector is controlled by means of the back-release relay 81 through'the next switch, with which latter connection is then established through 'thezprivate vwiper 53. It will benoticed that ,the vertical line relay 74 is connected to the nongrounded terminal of battery B, and that the rotary line relay 76 is connect-ed to ground; and the bridgecut-off relay 84 is provided to open the connection between the lineI relays 74 and 76.'and 4the battery terminals. This disconnection is desirable, because if the relays are not disconnected from the battery the ringing current for signaling the subscriber may operate either or both of the relays 74 and 76 and cause some interference with the switch. It is also desirable to remove the bridge formed through the said relays from across the line to give the voice-currents as clear a path as possible. Furthermore, the shaft 50 is provided with y a cam 85 which, when the shaft is in normal vertical position, permits the springs 77 and 78 to disengage; but on the firstvertical step of the shaft the cam 85 presses the springs into engagement. When the shaft is given a. rotary step, however, the cam 85 is carried out of engagement with the springs 78, and the springs 77 and 78 disengage. The switch shaft is provided with a normal arm 86 which, when the shaft is in normal p0'- sition,imaintains the spring 87 in contact with the contact point 88; but when the shaft is given one or more vertical steps the normal arm 86 permits the spring 87 to engage the grounded contact point 89, whereby a guarding potential is established at the rivate Vmagnet 79,

connector bank contact corresponding to the operati:i tocarrythesp 90(uponthe lendofwhichthereisallSDfromthe spring 92 and into n twlthvthe ,sgp

4same, although there `is mnteri chanical details of the r and connector,asiswellknown,areve muchthe dierence in the circuits. The connector switch shaft 122,1ikethelirst Mectorswitch shaft, carries the line wipers 123 4and 124 and the private wiper 125. The connector switch is also controlled by the calling subscriber thro themedium ofthe vertical androtary relays 126 and 127. The vertical Lline relay ,directly controls the vertical magnet128,andalsotherotarymagnet129and ggf relay 130. The function of the ver*- magnet g 128 is to give the shaft and shaft wipers their'vertical motion, and the rotarymagnet129impartstotheshaftand shaft .wipers a rotary or circuler motion. The rotary line rela 127 controls the prite u L l.; W .Ch httel', undr l" tain n.. 'tions, controls the release magn 132and alsothe side switch wipers 133, 134, 135, 136 and 137. The side switch 'of the connector, like the side switch of the firstselector, has a normal or iirst 'tio Ya second position and a third tion. e release magnet 132 is also controlled by the relay 138 whichisinturn the relay 139. By the condensers 140 an 141 the circuit thronghthe connector is divided into two sections, and the back-bridge relay 142, through which current is supplied to the called subscriber for talking isbridgedonthecalledsubscri ssldeo saidcondensers. Thereleaserelay139is similar to the relay 82 of the r C,and"whentherelay 139 isenergizedthe spring 144 (Fig. 11) is shifted out of ent with the spring 145 and into en- '.l tha 14 thenlocksthetwo in contad, and when the 139 deenergime, the locked are then bro y mtocoutactwith spring145,w an f- M Y circuit is elosedthrough the 'relay138;hutastheannature148nearsi nonna'lltgition thelatch147 comesinto contact the beveledv member 149, whereby the latch 147 is gradually pushed from the 1, end of the spring 146; and when the armatureisfullyrestoredthespringslandl are unlocked the spnng 144 returns to nonnal position out of nt with the spring 146. The central oce is :Tipped with a busy-signalling apparatus any suitable design, as, for example, the one comprising an interni' lloftheinduction-coiull52, whertby a usyeingarentis' ucedin esecondary--m|- ofthesaidcoil. Theconnector alsocarriesanormalpostarmgwhich whmtheconnectorshaftisonormaLallowsthespringltothecontact point 156. 'lhe substation' is like the rsulxetat:ionA., andtheswitchc' spring146. 'lllelatchsp' 144and146.

150inseries rotary line relay imei? switches to bring about this connection isas follows: When the subscriber removes the receiver 2 from the switch-hook 3, the springs and 11 close, and the sprin 6 and 8 close, and a circuit is thus establis ed includin the vertical and rotary line 4relays at t e selector C, and at the substation A the resistance coil 29 and the transmitter 12 in multi le. This circuit extends from ground G t rough the springs 157 and 158, rotaryline relay 75, side switch wiper 55, rotary line conductor 37, rotary im ulse springs 19 and 18 to .the spring 6, rom which the circuit branches, one branch extending through the primary winding 14,

transmitter 12, and springs 10 and 11 to the vertical line conductor 36; and the other branch extends through the springs 6 and 8, resistance coil 29, springs 32 and 33 to the vertical line conductor 36'. From the conductor 36 the circuit continues through the side switch wiperv 54, vertical line relay -74, springs 159 and 160 to the batte lead 161, and 'through battery B to groun G. As aresult both the vertical and rotary line relays o ratively energize.- The erates to placethe springs 162 and 163 in contact, whereby an energizing circuit is closed through the release relay 82. The circuit through the release relay 82 extends from ground Gz through the springs- 162 and 163, through the windin of the said relay to the battery lead 161, t ence through battery B to ground G. The relay 82 now energizes and operates to shift the spring 90 from the spring 92 to the spring 93, whereby the two springs 90 and 93 become locked, as previously explained.l The vertical line relay, upon energizing, presses the springs 162 and 164 into contact, thus closing an energizing circuit through the ver-V tical ma et 75. This circuit extends from ground 2 through the springs 162 and 164, through the vertical magnet to the battery lead 161, thence through battery B and to ground G; The vertical magnet bein energized operates to raise the switch sha 50 one step, placing the shaft wipers 51, 52 and 53 one step below the first level of the selector bank. When the dial is turned for the first digit 2. the springs 10 and l1 Separate, whereby the transmitter 12 is removed from across the line. As soon as the transmitter is thus removed from acrossthe line,

6, upon energizing. op-

me of the circuit that includes the line relays 74 and 76 at the selector C4 is increased, since the high resistance coil -29's Vretained across the line at the substation. Therefore,\the vertical line relay 74 weakens suiliciently to permit the armature to fall back, whereby the springs 162 and 164 separate. This curs when the dial is pulled down; then as the dial returns to normal position, thevertical impulse springs 16 and 17 are preed into contact twice, and' the rotaryV impulse plmgs 19 and 18A are separated once. en the springs 16 and 17 engage, the line conductors 36' and 37 aiethen short-cirvcuited, thereby shuntin or short-circuiting the resistance coil 29. hen the springs 16 and 17 e a new circuit is established through e substation A which includes only the vertical and rotar line relays 74 and 76. Since this circuit does not include the resistance coil '29, suiiicient current now flows in the circuit to operatively energize the vertical line relay 74. The springs 16 and '.17 being pressed into contact twice, the vertical line relay is again operatively energized twice, thereby pressin the springe 162 and 164 into contact and osing an energizing circuit each time through the vertical m et 75. This circuit extends from ground 2 through the springs 162 and 164, vertical magnet 5 to the battery lead 161, and through battery B to ground G. The vertical magnet being energized twice more 53 two steps to a position opposite the second bank level, which contains the terminals of t-he trunk lines leading to the Second-selector switches of the two thousand group. At the first vertical step of the shaft the switch shaft sprin 77 and 78 that are normally disengage arev pressed into contact by the cam whereby an energizing circuit is established through the private magnet 79. This ener izing circuit extends from ground Gz throug the springs 162 and 163, through the switch sha springs 77 and 78 fto the private magnet' 79 thence through said magnet to battery lea 161, and through battery B to ground G. When the rotary impulse tooth 24 separates the rotary impulse springs 18 and 19, the Vcircuit through the substation which comprises the vertical and rotary line relays in series with the resistance coil 29, is then broken, thereby permitting the rotary line relay 76 to momentarily vde-energize when the springs 18 and' 19 are disengaged.

`When the rotary line relay deenergizes, the springs 162 and 163 disengage, thereby breaking the energizing circuit through the however, being a slow-acting relay, is maintainedin its operated position while the energizing circuitis momentarily broken. As` soon as the impulse springs 18 and 19 again engage, the energizing circuit through the rotary line relay 76 is again estabhshed, and a ain the energizing circuit through the re ease relay 82 is established. When the side switch wiper 57 to the contact int 67, an energizing circuit is establis ied through the rotary magnet 80, said circuit extending from ground G contact point 67, side switch wiper 57 .mterrupter springs 165, thenoe'to the lead 161, and through battery B to ground G. The rotar magnet operates to carry the shaft and s iaft wipers in a rotary direction into contact with the first set of contacts of the second level. When the shaft is given its first rotary step the cam 85 asses out of engagement with the springs 77 and 78, whereby the Said springs disengage, breaking the energiz circuit through the private magnet; but i the first set ci.i contacts is busy, the private wiper 53 meets a guarding potential and a new energizing circuit is established through the rivate magnet 79, said circuit extending rom the grounded contact point to the rivate wiper 53, conductor 166, back-reease relay 81, side switch wiper 56, contact oint 66, private magnet 79 to the battery ead 161, and throug ,battery B to round G. Therefore, the side switch is loc ed in second position until the rotary magnet carries the wipers beyond the last busy' trunk line. When the last busy contact is passed over, the energizing circuit through the private magnet becomes broken, permitting the private magnet to be de-energized and the side switch to pass from second to third position, whereby the energizing circuit through the-rotary magnet 80 becomes broken as the side switch wiper 57 leaves the grounded'contact point 67. Also, when the side switch.wipers 54 and 55 engage the contact points 6 9 and 70, I'espectively, the .subscriber-s vertical and rotary line conductors 36 and 37 are extended to the trunk conductors 167 and 168, respectively, assuming that the shaft wipers 51 and 52 are in engagement with the contacts corresponding to the trunk conductors leading to the second-selector switch D. Of course, when the side switch passes to third position the line relays 74..and 76 are disconnected from the subscribers line, and the rotary line relay 76 deener as a result. When the rotary line re ay 76 deener izes, the springs 162 and 163 separate, ro en so t at the energizing circuit is through the release relay 82. lWhen the relay 82 de-energizes, the springs 92, 93 and 90 come'into contact, but since the side switch wiper 58 is in` third position this is from ground G* through the rotary linerelay 110, side switch wiper 103, ro

trunk conductor 168, shaft wiper 52, si e switch wiper to the rotary line conductor 37, through the substation, as previously traced, to the line conductor 36, side switch wiper 54, shaft wiper 51, vertical trunk conductor 167, side switch wiper 102, vertical line relay 109 to the battery i lead 161, and through battery B -to ground G. The relays 109 and 110 of the selector D are arranged like the relays 74 and 76 of the selector C that is, when the series circuit through the substation includes the resistance coil 29, the current-flow is not suilicient to operatively energize the vertical line rela 109, but is sufficient to operatively energize the rotary line relay 110; and when this series circuit does not include the resistance coil 29 the current-How is sullicient to operate the vertical line relay 109.

The rotary line relay, upon energizing, operates to close the springs 111 and 113 in contact, whereby an energizing circuit is closed through the release relay 114, in the manner explained in connection with the release relay 82 of the selector C. The energizing circuit for the said relay 114 extends from ground G*i through the springs 111 and 113 to the relay 114, thence through said relay to battery lead 161, and through battery B to ground G. It will be remembered that when the dial. returns to rest, after calling the first digit, the ratchet wheel 30 rotates one step in the manner previously explained. The operation of the dial for the second digit 2 causes the springs 16 and 17 to engage twice, and the springs 18 and 19 are disengaged once. The vertical line relay 109Voperates twice to close the springs 111 and 112 in contact which in turn close an energizing circuit through the vertical magnet 98. This circuit extends from ground (Jrs through the springs 111 and 112 to the -vertical magnet 98, thencev to the battery lead 161, and through battery B to ground G. The shaft wipers of the selector D are raised two steps and brought opposite the second level of the bank contacts which are the terminals of trunk lines leading to the connectors vof the two-hundred group of the second thousand. At the first vertical step of the switch shaft 107 the rivate magnet 101, like the private ma et 9 of the selector C, is energized at t e instant that the cam 119 presses the cam sprin 120 and 121 into contact. As soon as the circuit is closed the energizing current flows from ground G through the springs 111 and 113, through the cam sprin 121 and 120 to the private magnet 101, t ence through said magnet to the battery lead.161, and through battery B ground G. 0n the rotary impulse-that is, when the springs 18 and 19 are disengagedthe energizing circuit through the rotary line relay 110 is interrupted and the said relay deener izes, permitting the springs 111 and 113 to csengage, thus in turn breaking the energizing circuit through the private magnet 101 and the release relay 114. The release relay 114, being like the release relay 82 of the selector C, remains in its operated position until the energizing circuit is again established through te rotary line relay 110. But the private magnet, upon deener- 'zing, permits `the side switch to pass from lrst to second position, whereby the side switch wiper 105 engages the rounded contact point 169. The selector Iiow rotates in the same manner as the selector C to select the idle trunk'line leading to the connector E, and after the last busy contact has been passed over by theprivate wiper 118 the side switch passes to third osition, thereby breaking the circuit throug the rotary line relay and extending the subscriber s vertical and rotary line conductors 36 and 37 to the trunk conductors and 171 which lead to the connector E. When the circuit is broken through the rotary line rela 110 the s rings 111 and 113 fall apart, thus reaking the energizing circuit for the release relay 114. `The passa e of the side switch to third position noton accomplishes all this, but also, as soon as t e side switch wiper 104 engages the contact point 71', a guarding po- Vtential is established at the private wiper 118 for protecting the seized line against interference. Of course, it will be understood that by the operation of the dial for the second digit the ratchet wheel 30 at the substation is advanced a second step. When the side switch wipers 102 and 103 pass to third position' the series circuit including the r'otary and vertical line relays at the selector D and the resistance coil 29 at the substation A is broken, and a new series circuit is formed which includes the vertical and rotary line relays 126 and 127 of the connector E, energizing the latter. When the rotary line relay 127 ener izes, as stated, it places the springs 172 an 173 in contact, thereby closing va circuit through the release rela 139. This circuit extends from round through the springs 173 and `172, release relay 139, thence to battery lead 161, and

through battery B to ground G. The relay 139, upon energizing, operates to lock the springs 144 and 146 in contact, as explained. lVhen the vertical impulse springs 16 and 17 of the substation A are Ipressed into contact for the thirddigit the vertical line relay 126 is energized twice, and the springs 174 and are pressed onto the ground sp 173. The engagement of the s rings 174 an 173 closes the circuit throug the vertical magnet 128, said circuit extending from' ground G through the springs 173 and 174, side switch wiper 135, contact point 176,ver tical magnet 128 to the battery lead 161, and through battery B to ground G. The engagement of the springs 175 and 173 in the first instance also closes an energizing circuit through the rivate magnet 131, said circuit extending rom ground G through the springs 17 3 and 17 5, conductor 177, si e switch wiper 136, private m et 131 to the batte-ry lead 161, and throug'n battery B to ground G. The private magnet 131 energizes and places the springs 178 and 179 in contact, whereby a. lockin or retaining circuit is established throu i the private magnet. This circuit exten s from ground Y G through the springs 173 and 172, private magnet springs 178 and 179, private m et 131 to the battery lead 161, and through attery B to ground `G. The vertical ma et 128 being operated twice for the third digit, the connector shaft 122 and shaft wipers 123, 124 and 125 are carried two steps and brought opposite the level in which are located the terminals of the normal conductors leading to the line #2220. When the rotary impulse tooth 24 of the impulse wheel separates the springs 18 and 19, the energizing circuit of the rotary line relay 127 is broken, and the springs 173 and 172 momentarily disengage, whereby the retaining circuit through the private magnet 131 is broken. The private ma et de-energizes and permits the side switch to pass to second osition. Again it should be noted thatthet ird operation of the dial advances the ratchet wheel 30 at the substation another step. The o eration of the dial for the last digit (naught) energizes the vertical line relay 126 ten times, thus placing the springs 174 and 173 in contact ten times, whereby the rotary magnet 129 is operated to rotate the shaft wipers 123, 124 and 125 to the last contact of the second level of the connector bank. The circuit through the rotary m net 129 extends from ground G through :ge springs 173 and 174, side switch Wiper 135, contact oint 180, rotary ma et 129 to the battery ead 161, and througnbattery B to ground G. .Of course, when the vertical line ion' lll

relay is energized forthe lastdigit,andwhen the sprin 175 .engages the spring 173 at the irst impu se, the circuit through the private magnet 131 is again closed, and at the instant that said magnet energizes it again places the springs 178 and 1 9 in contact, again locking itself. When the rotary line relay 127 is d th f rivate m et e-energizes wi one o two gesults, mly'the so-called busy-release of the connector switch, lor the side switch a to third losition. It will be d,

that the atter result occurs. Then when tlhe side switch .wiprs 113g and 134 engage t e contact points 1 1 a 182, tively, the calling subscribers line conductors 36 and 37 are extendedto the normal conductors 183 and 184 which lead to the terminals of the called line #2220. When the siitt switch wiper181537 e the groun contact point a gua e l; potential is established at the connector ank to prevent any other subscriber from calling in on the same line. Also, thisclosing in contact of the wiper 137 and contact point 185 closes an energizing circuit through the cutoff relay 186 of the selector C. This circuit extends from the grounded contact point 185 to the side switch wiper 137, shaft wiper 125, normal conductor 187, normal sp contact point 189, through the cut-o relay 186 to the battery lead 161, and thro h battery B to ground G. When the sai relay 186 energizes it operates to disconnect the vertical line relay 7 4 from the nongrounded terminal of battery B, and the rotary line relay 7 6a from the grounded terminal of battery B, in order to Vprevent the called subscriber from operating his selector switch C when he answers. Itwill be remembered that as the dial returned tonormal position, after being operated for each digit, the ratchet wheel 30 is rotated one step; and since the dial was operated four times for the number 2220 the ratchet wheel 30 has been advanced four steps, whereby the bushing 31 carries the spring 32 out of engagement with the spring 35.

The disengagement of the springs 32 and 33 and the engagement of the springs 34 and 35, destroys, first, the series circuit through the substation, including the resistance coil 29, and establishes a new series circuit through the substation, including the primary winding and transmitter. This circuit extends from the vertical line conductor 36 through the push-button spring 26, contact point 27, springs 34 and 35 transmitter 12, primary winding 14, through the rotary impulse sprin 18 and 19 to the rotary line conductor 3 The resistance of the circuit through the substation, including the vertical and rotar line relays 126 and'127 ofl the connector is thus suicientlyreduced to permit the current-flow to operatively energize thev vertical line relay 126 of theV connector E. It shouldbe explained that the object in energizing the vertical line relay 126, as soon as the last operation of the e-energized for the last digit the f iss,-

Vgenerator conductors of the called line to-opcrate lscriber ceases to press the Y dial is completed is to- 'revent the relay 130 from eiier P To called subscriber, t subscriber presses the signalingbutton 25, whereby the spring 26 s-carried lout of engagement with t e contact point V27 and into t with the contact point 2S, whereby the resistance coil 29 is again .bri .acres the conductors 36 and 37 and e transmitter circuit removed. The resistance of the circuit including the vertical and line through the side switch wiper 135, springs Y 174 and 190, ringer relay 130 to the battery lead 161, and through battery B to `ground G. The ringer relay, upon energizing, operates to shift the spring 192 m the spring 193 to the spring 194, and to place the springs 195 and 196 in contact. BHy this operation the' ringer is bridged across the normal ringer 197 at the substation A. The ringing current passes from the ringer generator H through the springs 196 and'195 side switch wiper 133, contact point A181, shaft wiper 1%, normal conductor 183, vertical line conductor 198, condenser 199, ringer 197, springs 200 and 201, rotary impulse springs 202 and 203 to the rotary line conductor 204, normal conductor 184, shaft wiper V1%, contact point 182, side switch wi r134, ringer relay springs 192 and 194, bink to the ringer generator As soon as the ubutton 25 the spring 26 returns to norma position, thereby cutting theristance coil 29 out vof the circuit through the substation, and closing the circuit which includes the transmitter and primary winding. As soon as this second circuit is closed the vertical line relay 126 of the connector E re-energizes, thereby breaking the energizing circuit through the ringer relay 130. The subscriber at the called substation A', in respense to the signal removes the receiver from the switch-hook. When the receiver is up the cam-arm 205 permits the springs 206 and 207 to engage, whereby the primary windin 208 and transmitter 209 are bridged across e line conductors 198 and 204. The closing of these s rings also completes a circuit which provides the called substation with battery current for talking pu e a This circuit extends from the tact point 185, through the side switch wiper lll imi?

187, winding 210 of .the relay 142,`thence and 202, primary winding 208,- transmitter 209, springs 207 and 206, through the signaling springs to the vertical line conductor 198, normal conductor 183, shaft wi 123, side switch wiper 133 to the win 211 of the coil 142, thence to batteix@ lea `161, and through battery B Ato group G.

'Ihe circuit which provides the calling l subscriber with battery current for talki sprin cuit t rough a second re ease rela 138. This prposesextends from oundGthro p e rotary line relay 1 to the trunkconductor 171, shaft wiper 117 to the trunk conductor 168, shaft wiper 52 to the'rotary line conductor 37, thence through the rotaryimpulse sprin 19 and 18, primary winding 14, transmitter 12, sp 35' and 34, througlh the signalling springs to the vertical ne conductor 36, side switch wiper 54, shaft wiper 51, conductor 167, shaft wiper 116, trunk conductor 170, vertical line relay 126 to the battery lead 161, and through battery B to ground G. The two substations A and A' being thus provided with battery current 1 for talking purposes, conversation may be carried on over the circuits shown by heavy lines in Figs. 1 2 and 12. The release of the centra oce switching apparatus occurs when the calling subscriber opens up his line circuits by restoring-the receiver to the switch-hook. The subscribers line mayube opened up, if the subscriber hangs u 's receiver before the last operation of t e dial, by the separation of the substation sprin 6 and 8; but after the last operation o the dial the opening up of the circuit occurs when the springs 34 and 35 separate. The paration of the said springs 34 and 35, of course, occurs at the instant that the ratchet 30 is released Therefore, the release at this stage-that is, after the call' subscriber has established connection wit the called line-follows as a result of the separation of the s rings 34 and 35. The rotary linel relay 12 of the connector E now defener# gizes, thereby breaking the energizing circuit through the release relay 139,l whichY in turn de-ener 'zes and places the locked springs 144 an 146 in contact with the 145, ythus closi an energizing circircuit extends from ground through the relay 138, springs 146, 144 and 145 to the battery lea 161, and through battery B to ground Gr.` The release relay 138 upon energizing, closes the springs 212 and 213in contact, whereby a series vcircuit is closed through the release relay 115 of the second-selector D and the release magnet 132 of the connector E. This circuit ex- -56, release relay1 tends froml ground G" through the side switch wiper 104 of theselector D, release relay 115, shaft wiper 118, conductor 214, t through the springs 212` and 213, release `magnet 132 to the battery lead 161, and

through battery B to ground G. The connector release m et, uponjenergizing, op-

erates to restore t e connector switch shaft and side switch to normal position, at which time, also, the brid -cut-oE relay 186 .of the ,first-selector C eener es, re-` storing the line relas 74* and 76 to the contro of the calle subscriber. leaserelay 115 of the selector D, u on energizinghplaces the springs 215 an 216 in contact, erebyl closing a series release cir-v cuit including t e release relay 81 of the firstselector'C and the release magnet 100 of the second-selector D. This circuit extends from ground Gu through the side switch wiper 81, conductor 166, shaft wiper 53, throug the springs 216 and 215 of the release relay 115, release magnet to the batteiy lead 161, and throug battery B to un G. When the release magnet The reo the selector D energizes it attracts its armature 217, which latter operates to release the latch 218, whereb the springs of the release relah114 may he restored to normal position. e release armature 217, furthermore, assumes a position in which it is ready to release the selector switch D as soon as the release magnet 100 deenerglzes. The release relay 81, being also in t 's circuit, energizes and places the springs ,219"` and 220 in contact, whereby a et circuit is closed through the release magn 83 of the selector C. This circuit extends from ground G through the springs 220 and 219, through the magnet 83 to the battery lead 161 and through battery B to ground G. 's magnet operates to attract its armature 94, at which time the latch 91- is released and the springs 90 and 93 of the release rela 82 are unlocked. At the same time the re ease armature 94 assumes a po sition to release the switch C as soon as the release magnet-83 deenergizes. In the meantime, while the release magnets and rela s are being energized, the armature 148 o the release relay 139 of the connector E permits the latch 147 to strike the sloping 'member 149, thereby-releasing the spring 146 and as a result destroying the ener 'zin circuit of the release relay 138. aid re ay 138, of course, in turn permits the springs 212 and 213 to se arate, whereby t e trunk-release circuit t at includes the connector release magnet 132 and the backrelease relay 115 of the selector D is broken. The connector E is thus left fully restored,

and the release relay 115 ofthe selector D,

the release magnet 100 of the selector D i subscriber and of the back release relay 81 of the selector C. The release magnet 100 of the selector D then causes a restoration of the selector D, while the back-release relay 81 of the selector C, by breaking the energizing circuit of the release m t 83, causes the latter to release the sai selector C.

When the last rotary impulse was sent in from the substation by the subscriber, separating the sring 18 and 19, it was assumed that the ca ed 'ne was not busy and that the side switch tripped to third position; but if the desired line is busy a guardin potential protects it 'against intrusion, an if it is assumed that the ine #2220 is busy when the 5000 calls, asexplained, the busyrelease of e connector E follows as a result of the (le-energization of the rotary line relay 127 for the last digit. If the rotary magnet 129, in operating to carry, the shaft wipers Y onto the proper contact for the last digit, ro-

` private m will be evident that tates the private wiper 125 onto a busy or grounded contact, then whenthe rotary line relay 127 de-energizes and breaks the locking or retaining circuit through the private magnet 131, thisv ground potential is transmitted to the release magnet 132, when the et springs 221 and 222 engage, thus estab ishing an energizing circuit throu h the release magnet 132, said circuit exten ing from the grounded shaft wiper 125 through the side switch 2137,' contact point 223, private springs 221 and 222, release magnet 132 tothe battery lead 161, and through battery B to ground G. The release magnet, upon ene 'zi releases the connector switch sha an restores the connector side switch to its first position, returnin the vertical magnet 128 to the control o the vertical line relay 126. Since the busy-release occurs upon the last o eration of the dial, it v the time the side switch is restored to first position by the busy-release, the ratchet 30 at the substation has operated to disconnect'the high resistance vcoil 29 from the line, substituting instead the circuit throu h the springs 34 and 35. Evidently, therefre, the vertical and rotary line relays 126 and 127 will both energize simultaneously. As a result of the eneration of the vertical line relay 126, the s aft 122 will be raised and the private magnet 131 will again be locked. Of course, the locking of the private magnet at this time is simply incidental. When the subscriber now presses his signaling button 25 it simply has the effect of throwing the high resistance coil 29 in the line circuit, and as a result the vertical line rela 126 de-energizes each time it is thrown in; ut the only effect of this operation is that the shaft 122 will be raised one step each time, and this is also incidental. At the first vertical step of the shaft 122 the normal post arm 154.-4 leaves the spring 155, which latter then engages the -contact int 156 closing a busy-signalin circuit tough the substation, over which circuit a current flows from the busyv coilI 153. The calli subscriber upon`hearing the busy signal will understand that the line `is bus and upon restoring his receiver to his switch-hook will initiate the releasing of the switchin ready descri the only difference being `that the connector side switch is now in first instead ofthird position,- which, of course, p makes no difference. If the subscriber should y attempt to release at lthe end ofthe third jolperation, of the dial-that is, at a stage'in4 t e call where the "connector side switch is found in second position-the release of the switches is initiated, when the subscriber hangs his telephone on the switch-hook, by opening the subscribers line circuit at a point between the springs 6 and 8, this, of course, occurring meets the spring 8. If the subscriber should desire to release the switches after the first l operationV of the dialthat is, after the selector C has established connection with the selector D-or, as a matter of fact, at any as soon as the cam-arm 4 apparatus inthe manner alalsV time before the side switch of the selector D passes to third' position, he may release the selectors D and C by hanging up his receiver as usual, at which time the springs 6 and 8* will be separated and the line circuit broken in the manner already explained. y The rotary line relay 110 will, of course, deenergize, and the release relay 114 will also de-ene ize, and `as a result a release circuit is estab ished -comprising the release'magnet 100 and back-release relay 81 in series at the instant that the springs of the release relayy 114 come into contact. The release relay 81 will, of course, in turn cause the energization of the release magnet 83 of the selector C. The release magnet 100 of the selector D, upon energizing, releases the latch 218 of the release rela 114, breaking the trunkrelease circuit, an thus causing the restoration of all of the switches in the manner already ex lained.

The re ease relays 82, 114 and 139 maybe wound to any suitable resistance, but good results have been obtained when wound to a resistance of twenty-three hundred ohms; the vertical line relays 74, 109 and 126 to one hundred ohms; the rotary line relays 76, 110 and 127 to five hundred ohms; and the substation resistance coil 29 to three thousand ohms. v

It will be understood that the secondselector and connector'switches may be employed on a percentage basis. To illustrate specifically: In an automatic exchange of ten thousand capacity a somewhat common arrangement is to divide the subscribers and their allotted first-selectors into groups of thousands. Each thousand-group is subdivided into groups of one hundred. Then umm"l the like hundreds-#that is, the one-hundreds,

the two-hundreds, eter-of the various thou-` sands are arranged in groups, so that in a ten-.thousand system lthe one-hundreds of the thousands form one group, the two-hundreds selectors allotted to the thousands corre-l sponding to the level-that is, the secondselector-group of the first-selector first bank level is allotted to the first thousand, the second level to the second thousand, etc., thus taking care of the thousands. Furthermore, the second selector-groups of each thousand are arranged in, one group, and each bank level in each of these second-selector-groups has allotted to it a group of connectors, which in turn are allotted to the hundred of the corres nding thousand corresponding to the leve that is, the connector-group of the second-selector first bank level falls in .groups in the ten-thousands; also ten groups of second-selectors, one for each thousand; and ten groups of connectors in each thousand, one for each hundred. With this arrangement it will be understood that the rst level of the first hundreds in allv thousands in the system is multipledin a manner well understood. likewise the second level, etc. Also, all like levels of each second-selectorf group (one of which, as stated, is allotted to f each thousand)` are likewise multipled. In each of the aforesaid connector-groups, and

in the same manner, the like levels are ofv course, also multi led.

From the foregoing it will be seen that I provide a highly efficient common battery automatic telephone exchange system in which the lines are free from 'operating grounds outside of the exchange or central station-that is to say, which are f ree from ground connections at the substations for controlling the automatic switches. In this way I employ complete metallic circuits for both calling and talking purposes, and the current for controlling the automatic switches is derived from the same battery or batteries from which current is supplied y for talking purposes.

What I claim as my invention ist-'- 1. In a telephone system, telephone lines, automatic means including a pair of numerical progressively movable switches for extending connection from a calling one of said lines to a called one, successive circuits by which a calling subscriber controls said automatic means to extend a talking circuit to the called line, eachof said circuits includlscri ing the two sides. ofthe calling line in series, y

said automatic means comprising current feeding connections for supplyi talking current to the talking circuit, means for applyin said connections to the talking` circuit, sai connections normally disconnected from said lines.` I

2. A telephone system comprisin phone lines, an automatic connector go tendn connection from a calling line to a called ine, successive circuits for controlling said connector, each 1 circuit including the tw'o sides of the calling line in series, and

teleall the l means controlled at the connector for supplying all the talking current to the calling,l su

scribers line. 3. A telephone system comprising telehone lines, an automatic connector switch or extending connection from a calling line` to a called line; successive circuits for controlling said connector, each circuit including the two sides of the calling line in series, and means controlled at the connector for supglyin talking current to the called subrs ine.

4. In a telephone system, the combination of trunk lines, automatic trunk selectors, connectors for extending trunk line connections to the called lines, successive line circuits by whichl the calling subscriber oontrols one or more selectors and a connector to extend connection to the called subscribers line, each circuit including the two sides of the calling telephone line in series, andmeans controlledat the connectors for supplying all vthe talking current to the calling subscribers lines. f

5. A telephone system comprising a telephone line, an automatic trunk selecting switch. trunk lines, a metallic line circuit for controllingsaid switch to extend a talking vcircuit to another line via one of said trunk .restoring said switch by opening said telephone line, whereby the operation and the release of said switch is independentof the v earth at the subscribers station.

-switches for trunking a calling line into talking connection with a called line, successive circuits for controlling said automatic means, each circuit including the two sides of the callingline in series, tra-nsmitters inthe talking circuit, said automatic means comprising current feeding connections normally disconnected from said lines` means for supplying all the current to the talking circuit to charge the transmitters,

yand means for lreleasing the` connectionbetween the twol by openingk the circuit through the transmitter ofthe calling line.

7. AL telephone system comprislnu' telephonelincs, automatic means inclu in aI circuit includingI the two sides of the calling line in series, said automatic means ycomprising current feeding connections normallyy disconnected from said lines, transmitters for said lines, said automatic means com- `prising devices for ap lying said current ceding connections to t e talking circuit for supplying all the current to said transmitters `over said lines, and means for breaking the connection between the two lines by opening the circuit through the transmitter of one of the connected lines.

8. In a telephone` system, the combination of numerical automatic switches, metallic circuits for successively controlling a 'plurality ofsaid switches to extend a talking circuit between a calling and a called line, a central source of current for talking purposes, current feeding connections normally disconnected from the lines, said automatic switches comprising means for applying said connections to the talking circuit for supplyin all the current to the subscribers stations, romsaid source. l

9. In a telephone system, the combination of telephone lines, automatic connector switches less in number than said telephone lines, successive line circuits for controlling said connectors, each said circuit including the two sides of a callingl line in series, and means controlled at the connectors for supplying all the talking current to the telephone lines.l

10. A telephone system comprising a talk-v ing circuit, transmitters in said circuit, a

high resistance coil in'shunt of each transmitter` automatic switches, means for short circuiting said resistance coils to operate said switches, and a central source of currentsupply for furnishing talking current toV said transmitters.

11. In a telephone system, a calling line, a selector switch, means for extending a connection from said line to said selector, a trunk line, means for operating said selector to seize said trunk, an automatic. connector at the opposite end of said trunk, a called telephone line with which said connector is adapted to establishconnection, a pair of line relays in said connector for controlling its operation, a battery permanently bridged in series between said relays across the trunk line, and means for supplying talking current to the calling line through said relays from said battery. s

12. In a telep one system, a plurality of subscribers lines divided into groups, a

. SGCOD imei? lmatic connector switch connected to the oppositeend of said trunk, said connector havin one motion to select ou s and a motion to nd a cal ed ne in a selected group, a pair of line relaysin said connector for controlling its operation, a battery permanently bridged in series between said relays across said trunk, and

means for supplying talking current to the calling line through said relays from said battery. p

13. n a telephone system, a plurality of subscribers `lines divided into groups, a trunkI line, means including an automatic selector switch for extendin a connection from oneof said lines to sai Atrunk,.an automatic connector switch at the opposite end of said trunk, said connector having one mot-ion to select groups and a second motion'to connect with a called line in a selected grou a pair of line relaysin said connector or controlling its operation, a battery permanently bridged in series between said relays across said trunk line, and means for su plying talking current to the calling line t rough said relays from said battery.

14. n a telephone system, means for establishing a talking circuit between two lines, comprising a plurality of selectors each selector having quick and slow relays and a side switch having a plurality of itions, release circuits, means controlle by said slow relays when energized for maintaining said circuits open, means whereby saidlslow relays may release said switches while the said switches are in first or second l position, and a centralized battery for operating and talkin purposes.

15. In a telep one system, means for establishing a talking circuit between two points comprising selector switches, a slow acting relay and a quick-acting back-release relay in each switch, aside switch, any one of said switches having three operative positions, a release circuit, means controlled by one of said slow relays when energized for maintaining said circuit open, means whereby said slow acting relay may release said selector while said side switch is in first or second position, means whereby said quick actin relay may release said switch after the side switch passes to third position, and a central battery for supplying current for operating and talking purposes.

16. In a telephone exchange system, a subscribers line, a transmitter, a calling mechanism, a ratchet wheel, a dial for operating said wheel. a resistance coil normally in bridge of the line, means whereby said resistance coil is disconnected from the line bv the operation of said wheel and the transmitter bridged across the line at the same time, and switching Ameans responsive to said mechanism.y

17. In a telephone system, a subscribers line, an automatic substation on said line, suitable calling mechanism comprising a ratchet device provided with a pawl, an o erating dial, means whereby said ratchet evice is advanced one step for each operation of the dial, said ratchet held by said pawl at each step and adapted to be released when the receiver is restored to the switch hook and carried into normal position, and switching means responsive to said mechanism. v

18. In a telephone exchange system, a subscribers line, an automatic substation on said line, a suitable calling mechanism at said substation comprising a high resistance coil adapted to be bridged across the line when the switch hook rises, a ratchet device adapted to be operated step by step on the transmission of a call, means whereby said resistance coil is disconnected from across the line at the last step of the ratchet device, additional means for temporarily bridging said resistance coil across said line, and an automatic switch cont-rolled thereby.

19. In a telephone exchange system, a subscribers line, an automatic substation on said line, a suitable calling mechanism, means whereby the transmitter of said substation is adapted to be bridged across the line when the switch hook rises, astep-bystep ratchet device for use in transmitting a call, means for opening said transmitter the operation of said dial,

bridge durin means upon tl e last operation of said dial to again close said bridge, ands'witching means responsive to said mechanism.

20. A telephone system comprisin telephone lines, an automatic connector or extending connection from a calling line to a called line, provided with means having vertical motion to select groups and rotary motion to connect with a line in the selected group, successive circuits for controlling said connector, each circuit including the two sides of the calling line in series, and means controlled at the connector for .supplying all the talking current to the calling subscribers line. y

21. A telephone system comprising telephone lines, an automatic connector switch for extending connection from a calling line to a called line, provided with means having vertical motion to select groups and rotary motion to connect with a line in the selected group, successive circuits for controlling said connector, each circuit includf tors, connectors for' extending trunk line connections to the, called lines, provided with .means having vertical motion to sef 23. 4In a telephone system, the combina.

tion of a telephone line, acentral source of talking current, means for controlling the supply of talklng current tothe telephone line, trunk lines, an individual trunkingswitch for said telephone line provided with means having vertical motion to select groups and rotary step-by-step motion to connect with av line in the selected grou and a pair of circuits for controllin bot the` operation andthe release of sald individual switch, each circuit includin the two sides of the telephone line in series.

24. A telephone system comprising a telephone line, an automatic swltch provided with means having Vertical step-by-step motion to select groups and rotary motion to connect with a line in the selected group, a plurality of magnets in said switch; a central source of current for supplying all the talking current through sald magnets to the calling and called telephone lines, a complete metallic line circuit for controlling said switch, means for signaling the called subscriber, and means for releasing or restoring said switch by opening of the telephone line, whereby both the operation and the release of said switch is independent of the earth at the subscribers station.

l25. In a telephone system,`the combination of telephone lines, automatic connector switches less in number than said telephone lines, provided with means having vertical motionto select groups and rotary Vmotion to connect with a line in the selected group, successive line circuits for controlling said connectors, each said circuit including the two sides of a calling line in series. and means controlled at the connectors for supplying all the talking current to the telephone lines.

26. In a telephone system the combination of subscribers lines, su cribers individual trunkingl switches, automatic connector switches less in number than the subscribers lines, provided with means having vertical motion to select groups and rotary motion to connect with a line 1n the selected oup, metallic line circuits for controlling t e individual switches and the connectors, each said line circuit including the two sides of a calling telephone line in series, and

. groups and rota motion to connect with a line in the cted group, means for short-circuiting said resistance coil to op-A 'crate said switches, and a central source of current supply for furnishing talking cur` rent to saidtransmitters.

28. Ina telephone system, afcalling telephone line, a trunk line connected -therewith, an automatic connector at the end of said trunk line, provided'with means having vertical lmotion to select groups and rotary motion to connect with a line in the selected group, a called telephone line teinporarily seized by` said connector, a pair of line relays in said connector, a battery permanently bridged in series between said relays across the Mtrunk line, and a transmitter inthe line of the calling subscriber, said transmitter receiving talking current rom said battery over said permanent bridge.

29. In a telephone system, a calling telephone line, a trunk line, an automatic connector aty the'end of said trunk line, provided with means having vertical motion to select groups and rotary motion to connect with a line in the selected for connecting the tele hone line with the trunk line, a called te ephone line temporarily seized by said connector, a air of electroma ets permanently bridge across said trunlline, a battery permanently connected in series between said electromag- Vnets, a transmitter in the line of the calling subscriber, and means for supplying all the talking current to said transmitter `from said battery over said bridge.

30.`In a telephone system, the combination of a telephoneI line, a central source of talking and controlling current, meansfor controlling the supply of talking current to the telephone line, trunk lines, an individual trunking switch for said telephone line provided withmeans having verticali motion to select groups and rotary motion to connect with a line in the selected group',

- calling mechanism requiring a se rate manual o ration thereof for each digit of the calle number, operative to transmit suitable controlling current for one digit beforetlie said mechanism is manually operated for the next digit, and a plurality of diferent circuits for controlling both the operation and the release of said individual switch, each circuit including said mechanism and the two sides of the telephone line in series.

roup, means l naar:`

to transmit suitable controlling current for i one digit before the said mechanism is manually operated for the next digit, and a transmitter in the line of the calling subscriber, adapted to receive talking current from said battery through said bridge.

32. In a telephone systemya calling telephone line, a trunk line connected therewith, a numerical automatic connector switch at the end of said trunk line pro` vided with means having vertical motion to select groups and rotaryv motion to con- 'nect with a line in the selected grou a called telephone line temporarily seized) by said connector, a pair ofl ine relays in said connector, a battery permanently bridged in series between said relays across the trunk line, calling mechanism requiring a separate manual ,operation thereof for each digit of the vcalled numberyoperative to transmit suitable controlling current for one digit before the said mechanism is manually operated for the next digit, and a transmitter in the line of the calling subscriber, said transmitter receiving `talkin current from said battery v through sai relays.

33. In a telephone system, a calling telephone line, a trunk line, an automatic connector at the end of said trunk line, provided with means having vertical motion to select groups and rotary motion to connect with a line in the selected 1group, means for connecting the telephone ine with the trunk line, a called subscribers telephone -to receive talking current from said battery through said electromagnets.

34. In a telephone system, the combina.- tion of a plurality of switches each adapted for both vertical and rotary step-by-step of said triink line motion, in response to oneV or more impulses `for the called number, telephone lines', suclcessive line circuits for successlvely'controlling the said switches to extend connection from a calling line to a called line, said line 'poses also.

35. In a telephone system, the combinai tion of trunk-lines, an automatic step-bly;-

step trunking switch provided with trun selecting mechanism, `and with releasing mechanism, a telephone line, a subsci'ibers releasin device for saidtelephone line, successive ine circuits for` controlling the opcalling subscribers line,

eration of said switch, said circuits each including the two sides ofthe telephoneV line in series, the release mechanism of said' switch being directly7 responsive to a sub scribers releasing dev1ce, and means fon' `supplying current over the telephone line to operate said switch, and `for talking purposes also.

36; In a. telephone system, a plurality of subscribers lines, means including automatic switches controllable over two sides of the line circuit in series for establishing connection between said lines, a source-of ringing current, means for increasing the resistance on the calling line, and means controlled by said increase of resistance for connecting said ringing current with. the

-called lin 37. In a telephone system, a plurality of subscribers lines, meansy including automatic switches controllable over two sides of the line circuit in series for establishing connection between said lines, means for increasing the resistance of said connection, a source of ringing current normally disconnected from the called subscribers line,

and means controlled by said increase of' resistance for connecting said ringing current with the called line.

38. In a telephone system, a plurality of subscribers lines, means includin automatic switches controllable over two sides of the line in series for establishing connection between two of said lines, a push button at the means controlled by said push button for increasing the resistance on said line, a source of rin ing current, and means controlled by sai of resistance for connecting said ringing current with the called line.

39. In a telephone system, a switch having a movable contact arm, means for releasing tlie same including-a release magnet and a relay slow to release its armature, said rela controlling the release magnet during t e time said switch is ci rating to move said contact arm, a quie -acting relay relay controllin `said selector,

increase controlling vthe release magnet after the switch has operated independently of said slow relay, and a central source of talking and operating current for said system.

40. In a telephone system, a trunk, a switch for extending connection thereto, releasing. means for said switch includi a relay slow to release its armature, sai

the release continuously after the operation of the switch is started and until connection is extended to the trunk, a quick-acting relay controlled over said trunk .for controlling the release after `the switch has established the connection, and a central source of talking and operating current for saidl s stein. i v

41. In a telephone system, a trunk, a. switch for extending connection therefrom, releasing means for said switch including a releaseinagnet and a relay slow to release its armature, said relay controllin the release magnet continuously throng out the time the switch isfoperating, a quick-acting vrelay controlling the release magnet after connection has been established from the trunk independently of said slow relay, and -a central source of talking and operating current for said system.

42. In a telephone system, means for establishing a call, means for releasing the call including a release magnet and relays slow to release their armatures, said rela s controlling the releasemagnet continuous during the establishment of the call, nick acting relays for controllin the re ease magnet during conversation lndependently of said slow acting relays, and a central source of talking and operating current for said system. l

43. In a telephone system, a calling and a called line, a selector switch and a connector switch, means for controlling the selector over thecallin line to select said connector and extend te calling line thereto, means for controlling said connector over the calling line to extend the connection to said called line, means in said connector for supplying talking current to the calling and called lines, a release magnet in a slow acting relay controlling said release magnet throughout the selecting operation o said. selector, and a quick acting relay controlling said release magnet independent of said slow relay after the calling line has been extended to said connector.

44. In a telephone system, acalling and a called line, a selector switch and a connector switch, means for controlling the selector over the calling line to select said connector and extend the calling line thereto, means for controlling said connector over the callin line to extend the connection to said ca led line, means in said connector for supplying talking current to the calling and Alois i called lines, a release magnet in said selector,

.a slow acting relay controlling said release magnet throughout the selecting o ration of said selector, a quick acting re ay contro said release magnet independent of sai slow relay after the calling line has been Aextended to said connector, a circuit for said quick relay extending between the selector and connector, and means in the connector controlled by the calling subscriber for controlling said circuit.

45. In a telephone system a callin `and a called line, a train of seria rela n automatic switches for connectingsaid lines, means includin a line relay in each switch for o rat' -t e samea control circuit for each e re y including the two talking Vconductors of the calling line in series,

' means in veach switch except the last for' disconnecting its associated line relay from the calling line as soon as the switch is operated, means in the final switch for suppl ing talking current to the calling and ca ed lines, trunk release circuits independent of the talking conductors for releasing all said switches exce t the last, and means in the final switch or controlling said release cir cuits.

46. In a telephone system, a calling and a callui line, a selector switch having two line wipers and a test wiper, means including a line relay in said" selector directively controlled over the two conductors of .the calling line in series top the switch to extend a connection toward the called line, means'for disconnecting the line i relay\from'the line when the switch is operated other switching mechanism then controlled over the two talking conductors of the calling line in series to complete the connection to the called line, the control circuit for said other switching mechanism including the line wi rs of said selector, means in one of said other switching mechanisnis for supplying talking current to the calling line over a circuit includ' thetwo line wipers of said selector, and a circuit for releasing said first selector .including said test wilper. v

47. n a telephone system, a step by step switch having a'movab e contact arm, means for releasing said switch including a release magnet and a relay slow to release its armature, said relay controlling the release magnet throughout the `time said switch ris operating to move said contact arm a plurality of steps, a quick acting relay controlling the re easem et after the switch has operated indepen entl ofsaid slow relay, and

a central source o talking and operating'A current for said system.

Signed at Chicago, Illinois, this 26th day of August1920.

RAYMOND H. BURFEIND. 

